> Markets can't decide "families can have only one child"
Actually they can. It's part of the reason why a lot of capitalist nations are seeing major problems with population stagnation and possibly shrinkage.
The problem is markets don't care at all about society. If they can require that every member of a household has to work and extract all their money as efficiently as possible, then they leave little room for society to have families.
Capitalism is geared towards minimizing workers' free time. And, unfortunately, free time is how babies get made and kids get raised.
That is where western capitalism is failing. Shouting louder and young adults to pull on bootstraps harder isn't making them have kids in their studio apartments.
South Korea and Japan are 2 examples of this train-wreck that's coming for the US and other nations.
> If they can require that every member of a household has to work and extract all their money as efficiently as possible, then they leave little room for society to have families.
This ascribes an agency to capitalism that doesn’t exist.
The families themselves make the choices to have more or fewer children.
Capitalism says nothing about free time. Make the connection in your argument - people without enough money work as much as they can, maybe… but I still don’t see the lower wage people I know working 16 hour days. In fact it is the people who have a use for the extra money, usually to buy free time later, as one would expect in a capitalistic system.